Influence of dipping time on uptake of preservative solution, adsorption, penetration and fixation of copper-ethanolamine based wood preservatives

Copper-ethanolamine based wood preservatives are the most important products for protection of wood in use class III and IV applications. These preservatives can be applied using different procedures. One of them is dipping, a method which is predominantly used in less industrialised countries. The most important parameter, that influences the quality of this treatment, is dipping time. Influence of various dipping times on copper retention, adsorption, penetration, colour of the specimens and copper fixation was examined. In this paper copper-ethanolamine solutions of two different concentrations were utilised (c_Cu=0.05% or 0.25%). The results showed that longer dipping treatments resulted in higher uptakes of preservative solution, better penetrations and lower leaching of copper-ethanolamine based wood preservatives from Norway spruce wood. After one week of dipping, samples retained on average 275 kg/m³ of preservative solution, copper active ingredients penetrated on average 3 mm into the specimens, and only 2.3% of copper was emitted from wood impregnated with aqueous solution of the higher concentration, when subjected to ENV 1250 leaching procedure.     

Performance of wood impregnated with N-methylol and copper based aqueous solutions

The combination of copper and N-methylol compounds considerably improves the performance against copper sensitive fungi (G. trabeum and T. versicolor), while the fungicidal effect against copper tolerant strain (A. vaillantii) remained insufficient. Addition of N-methylol compounds to copper solution significantly reduces leaching from wood blocks impregnated with the solution of the lowest copper concentration (c_Cu =0.1%), and less notably reduces leaching from wood blocks impregnated with solutions of higher copper contents (c_Cu=0.5%).     

Performance of wood impregnated with N-methylol and copper based aqueous solutions

The combination of copper and N-methylol compounds considerably improves the performance against copper sensitive fungi (G. trabeum and T. versicolor), while the fungicidal effect against copper tolerant strain (A. vaillantii) remained insufficient. Addition of N-methylol compounds to copper solution significantly reduces leaching from wood blocks impregnated with the solution of the lowest copper concentration (c_Cu =0.1%), and less notably reduces leaching from wood blocks impregnated with solutions of higher copper contents (c_Cu=0.5%).     

Improving the UV and water-resistance properties of Scots pine (Pinus sylvestris) with impregnation modifiers

Wood modification is commonly used to alter and improve wood properties. This study investigates the effects of impregnation modification with four environmentally nontoxic agents on the UV-resistance and water absorption properties of solid wood. Scots pine (Pinus sylvestris) was impregnated with modifiers by pressure device. The solid wood specimens were treated with water glass, silicone, melamine, and tall oil. The modified samples were analyzed by SEM microscopy, and thickness swelling, water absorption and UV resistance were determined. The penetration of the studied modifiers differed. The melamine-treated samples were found to exhibit the best impregnation, which also affected the wood properties favorably. The melamine-treated solid pine wood samples absorbed half of the water absorbed by wood treated with the other solutions and attained the best results in thickness swelling and weathering tests. It is concluded that impregnation modification of Scots pine is dependent on the nature of the modifier and based on the results of this study, melamine solution treatment is found to have a positive effect on the properties of solid pine wood.     

Improvement of fungicidal properties and copper fixation of copper-ethanolamine wood preservatives using octanoic acid and boron compounds

Copper ethanolamine preservatives are one of the most important solutions for wood preservation. As copper itself can not ensure sufficient protection against wood destroying organisms we combine it with other co-biocides like quaternary ammonium compounds, azoles and/or boron. Influence of different boron compounds and octanoic acid on copper fixation as well as performance of spruce wood impregnated with different copper/ethanolamine/boron based aqueous solutions is described in this paper. Copper fixation was determined according to the modified ENV 1250 (1994) standard method, while performance against Antrodia vaillantii, Gloeophyllum trabeum and Trametes versicolor was tested according to the mini block procedure. The results showed that addition of boron increases copper leaching, but on the contrary improves performance against wood decay fungi. On the other hand, addition of octanoic acid improves copper fixation, and slightly decreases resistance against copper tolerant fungi.     

Utilisation of chemically modified lampante oil for wood protection

Within the Slovenian region of Istria, the olive growing and oil production industry is strong. This industry has a long history and the olives grown here have high levels of biologically active compounds including a variety of phenolic compounds. Using residual materials generated by this industry in potential wood protection systems would not only valorise low-value materials and stimulate rural economies but would also provide an alternative to currently used oil-based protection systems. The objective of this study was to produce an oil treatment for wood protection and assess its efficacy in reducing leaching, weathering effects, and fungal decay. Two maleinisation techniques were used to chemically modify low-value lampante oil in an attempt to limit leaching when impregnated in wood. Pinus sylvestris (Scots pine) and Fagus sylvatica (European beech) were treated with the modified oils and underwent leaching, accelerated weathering, and decay tests. Leaching of the treatment oils was relatively low compared with other experiments and beech wood specimens treated with a direct maleinisation treatment showed improvement in performance compared to control specimens. In addition, it was found that the modified oils were not completely removed from the wood after solvent extraction indicating that they could potentially be used as an immobilisation agent in combination with other treatments thereby reducing the amount of active component of the protective agent.     

Relative leaching and aquatic toxicity of pressure-treated wood products using batch leaching tests

Size-reduced samples of southern yellow pine dimensional lumber, each treated with one of five different waterborne chemical preservatives, were leached using 18-h batch leaching tests. The wood preservatives included chromated copper arsenate (CCA), alkaline copper quaternary, copper boron azole, copper citrate, and copper dimethyldithiocarbamate. An unpreserved wood sample was tested as well. The batch leaching tests followed methodology prescribed in the U.S. Environmental Protection Agency toxicity characteristic leaching procedure (TCLP). The wood samples were first size-reduced and then leached using four different leaching solutions (synthetic landfill leachate, synthetic rainwater, deionized water, and synthetic seawater). CCA-treated wood leached greater concentrations of arsenic and copper relative to chromium, with copper leaching more with the TCLP and synthetic seawater. Copper leached at greater concentrations from the arsenic-free preservatives relative to CCA. Arsenic leached from CCA-treated wood at concentrations above the U.S. federal toxicity characteristic limit (5 mg/L). All of the arsenic-free alternatives displayed a greater degree of aquatic toxicity compared to CCA. Invertebrate and algal assays were more sensitive than Microtox. Examination of the relative leaching of the preservative compounds indicated that the arsenic-free preservatives were advantageous over CCA with respect to waste disposal and soil contamination issues but potentially posed a greater risk to aquatic ecosystems.     

Kupfer-HDO—ein vielseitiger Wirkstoff im Holzschutz

Favourable toxic values of the water-insoluble effective substance Bis-(N-Cyclohexyldiazeniumdioxy)-copper, CU-HDO, for wood-destroying basidiomycetes and soft-rot resulted in the development of water-soluble, chromium-free wood preservative products. Biological tests of water-born formulations based on Cu-HDO showed threshold values after leaching, considerably lower than the values of conventional copper-/chromium-containing wood preservatives, especially for brown rot fungi. Examinations in application engineering with pine and spruce timbers indicated that penetration and distribution of the wood preservative come up to the requirements of an application in hazard class 4. Toxicological values and data on environmental aspects, especially concerning disposal of the impregnated wood, show that this formulation is an interesting alternative to wood preservatives based on conventional copper/chromium compounds.     

Induction of Vesicle Formation by Exposing Apple Tissue to Vacuum Impregnation

This paper demonstrates that vacuum impregnation of mature apple tissue in the presence of different sugars results in the formation of membrane vesicles inside the cells. Vesiculation is regarded to be a metabolic consequence of the impregnation process. Vesiculation is shown when the endocytic marker FM4-64 was impregnated into the apple tissue together with the sugar solutions. Vesicles were formed at the plasma membrane already 30 min after impregnation and remained inside the cells for at least 24 h, a metabolic process that was inhibited in the presence of chloroquine, a specific endosomic inhibitor. This phenomenon was not dependent on the osmotic strength when sucrose was used for impregnation. However, the vesiculation drastically dropped when a hypertonic trehalose solution was impregnated. We suggest that the impregnated sugars may not totally remain in the extracellular space between the cells, as normally believed, but at least a fraction might be incorporated into the cells.     

Possibilities for compositional tailoring of Norway spruce (<Emphasis Type="Italic">Picea abies</Emphasis> L. Karst.) wood using a hydrophobic oil impregnation process

Zusammenfassung Impregnation with hydrophobic oils offers non-toxic options for preserving Norway spruce (Picea abies L. Karst) wood that could potentially be used to tailor the properties of wood products, especially those used in exposed conditions. The objective of this study was to quantify the effects of the water-filled porosity and density of Norway spruce wood and treatments (applied to set the wood’s water contents at desired test levels) prior to impregnation with the linseed oil derivative Linogard by the Linotech process on its oil retention. Retention of oil differed significantly between tissue types. Dried specimens always retained less oil than corresponding undried or rewetted specimens. Furthermore, water-filled porosity and density had significant effects on oil retention levels within tissue types, allowing linear regression equations to be developed that gave good predictions of oil retention parameters for different tissues, with R² values ranging from 0.66 for mature heartwood to 0.85 for mature sapwood. Thus there is scope to use hydrophobic oil impregnation processes for producing compositionally tailored wood materials with specified properties.     

Improvement of termite resistance,dimensional stability and mechanical properties of pine wood by paraffin impregnation

Paraffin has been used as surface protection of wood throughout the ages but its use for impregnation to improve wood resistance to biodegradation is recent. This study determined the main improvements on wood properties with paraffin impregnation. Healthy Pinus pinaster Ait. wood was impregnated with paraffin at different levels using a hot–cold process. Weight gain, equilibrium moisture content and dimensional stability (ASE) at 35 and 65 % relative humidity, termite durability against Reticulitermes grassei (Clément), bending strength, bending stiffness (MOE) and Janka hardness were determined. Density increased from 0.57 to 0.99, ASE ranged between 38–96 % and 16–71 % for 35 and 65 % relative humidity, respectively. Equilibrium moisture content decreased from 9.9 and 12.0 % to 0.8 and 3.6 % for 35 and 65 % relative humidity. Termite durability improved from level 4 to level 3 of attack, and higher termite mortality was found in treated wood (52 % against 17 %). Bending strength (MOR) increased with paraffin weight gain, reaching a 39 % increase. MOE also increased by about 13 % for wood with a weight gain around 80 %. Janka hardness increased significantly reaching about 40 % for wood with 80 % weight gain. Paraffin impregnated wood has improved properties with regard to equilibrium moisture content, dimensional stability and density, bending strength and Janka hardness, and resistance against termites.     

Vergütung von Kiefern- und Eichenholz durch Tränkung mit Harnstofformaldehydharz

Wood specimens of oak and pine have been impregnated with urea-formaldehyde-resin by the full-cell process. The treated wood was tested with respect to its water repellent and its strength properties as compared to untreated wood specimens. The hydrophobic effect in pine and oak was determined after a storage under water. Additionally, a possible increase of crushing and bending strength was measured with pine. As a result it can be stated that impregnation with a urea-formaldehyde-resin presents an effective system to protect wooden building elements.     

Effect of <Emphasis Type="Italic">Punica granatum</Emphasis> peel and <Emphasis Type="Italic">Melia azedarach</Emphasis> bark extracts on durability of European beech and maritime pine

A method to improve wood durability using natural extracts was evaluated. Wood deterioration is a condition caused by several abiotic and biotic factors including fungal contamination. To date, approaches aiming at the reduction of these contaminants mainly involve the use of chemicals agents. Natural products could represent an alternative strategy. Aqueous extracts of Punica granatum L. (pomegranate) peel and Melia azedarach L. barks were evaluated as antifungal agents to improve natural durability of beech wood and maritime pine. To evaluate the effect of treatments under simulated accelerated ageing of wood by natural conditions, impregnation and leaching tests were performed. Results demonstrated that samples impregnated with pomegranate or M. azedarach solutions notably increased the biological resistance of wood in a dose-dependent manner. These results were confirmed by the reduction in weight losses in treated samples even after 6 weeks of fungal exposure. Moreover, after leaching tests, 20 and 7% (w/v) of pomegranate and M. azedarach extract solutions were demonstrated as the better concentrations to enhance wood durability. Total phenol content and characterization of the phenolic compounds in both, natural extracts and wood samples were analyzed by Folin–Ciocalteu assay and HPLC-DAD. In conclusion, it was demonstrated that the present method can be considered as an effective treatment to increase wood durability while it proposes the valorization of natural extractives in wood industry.     

Zur Prüfung und Bewertung der Umweltverträglichkeit von Holzschutzmitteln

Wood preservation can be made more environmentally compatible (1) by confining the use of wood preservative chemicals to the necessary minimum, and (2) by the use of effective and at the same time environmentally compatible wood preservatives. The aims and main points of testing and evaluating the environmental compatibility of wood preservatives are described. Crucial in this concern is the emission rate of the active ingredients of the wood preservatives (which leave the impregnated wood by leaching or evaporation), and this rate should be as low as possible for reasons of both long-term efficacy and low environmental load. The main pathways of possible environmental input of the active ingredients are leaching and evaporation during storage, transport and use of the impregnated wood and the input of their components or decomposition products during waste management. Looking at the leaching of non-fixing, not yet fixed as well as fixed wood preservative salts and organic active substances some problems arising in the practice of wood preservation and in the evaluation of the environmental compatibility of wood preservatives are dealt with and possible solutions are demonstrated.     

Feasibility study of utilization of commercially available polyurethane resins to develop non-biocidal wood preservation treatments

Evaluation of commercially available polyurethane resins used up to now for coating applications to develop non-biocidal wood preservation treatments has been conducted. A simple method of vacuum impregnation of these resins into beech wood (Fagus sylvatica L.) and pine wood (Pinus sylvestris L.) samples followed by varied curing processes at ambient temperature, 103, and 200 °C has been performed. Based on the analysis of weight percent gain before and after leaching, treatment resistance to leaching, anti-swelling efficiency, wettability and decay durability measured for treated and untreated blocks after leaching with the white-rot fungus Coriolus versicolor for both wood species and the brown-rot fungi Poria placenta and Gloeophyllum trabeum for pine wood, it can be concluded that such treatment can be considered as potential valuable non-biocidal treatments.     

Wood surface stabilization

The interaction between wood,Pinus sylvestris (60% RH), and polyethyleneglycol (PEG) of different molecular weights (PEG 200 and PEG 1500), pentaerythritol and glycerol, impregnated into wood, has been investigated using Scanning Electron Microscopy (SEM), dynamical mechanical techniques (DMTA), X-ray diffraction (WAXS) and macroscopic dimensional measurement. Reduced dimensional changes after impregnation, in environments with changing moisture content, show that the stabilization effect of glycerol impregnation is very good. The other chemicals used, especially pentaerythritol, were not as effective as glycerol. Cell wall measurements, using SEM, show that an increase in cell wall thickness gives a corresponding increase in stabilization effect. DMTA-measurements show that interaction between wood molecules and the chemicals used differs. In general, a higher degree of cell wall penetration of the chemicals show a better stabilization effect. PEG 200 was found to penetrate the cell wall much better than PEG 1500. WAXS-investigations show free crystalline pentaerythritol, PEG 1500, glycerol and PEG 200.     

Effect of hot air post-treatments on copper leaching resistance in ACQ-D treated Chinese fir

Chinese fir (Cunninghamia lanceolata Hook.) wood cubes (19?×?19?×?19 mm³) were treated with amine copper quat-type D (ACQ-D) solution and fixed with different hot air post-treatments. The effects of temperature, relative humidity, duration, air circulation of post-treatment as well as the copper retention in the treated wood on copper leaching were investigated. With the help of ultraviolet or visible spectroscopy (UV/VIS), the valence conversion of copper in treated wood post-treated with optimal post-treatment conditions was investigated, and its relation with copper leaching was also discussed. The results showed that besides temperature and relative humidity, air circulation during hot air post-treatments also had a significant effect on accelerating copper fixation in ACQ-D treated wood. 70 °C, 80% R.H. with good air circulation provided a suitable condition for complete fixation of copper in a short period. After the applied post-treatments, up to 11.3% cupric copper reduced to cuprous form. A higher copper conversion rate usually corresponds to lower copper leaching, which is consistent with the contribution of lower water solubility cuprous copper.     

Mechanical properties of wood treated with PF-pyrolytic oil resins

Jack pine and sugar maple wood samples were treated in a two-step process that involved first a copper chloride or a copper chloride-sodium borate mixture and then a phenol-formaldehyde resin containing a certain percentage of softwood bark pyrolytic oil. Various controls were also prepared for comparison. The modulus of rupture (MOR) of jack pine samples was generally negatively affected by the treatment, the observed values being lower than those of the controls. These values were statistically lower or equal to those of untreated samples. On the other hand, the modulus of elasticity (MOE) of treated jack pine samples was not found to be statistically different from that of the untreated wood. Mechanical properties behaved in a similar way for sugar maple wood. Unlike the other treatments, copper chloride–sodium borate and the resin containing 85% of pyrolytic oil as phenol substitute appeared to slightly improve the mechanical properties of both wood species even if not significantly so. Treatment with PF-pyrolytic oil resin resulted in similar or slightly better mechanical properties when compared to CCA-treated wood. The amount of treating water soluble salts retained in samples after the first treatment had a significant impact on MOR of both wood species and on MOE of sugar maple.     

Möglichkeiten zur Herabsetzung der Umweltbelastung durch organische Lösungsmittel aus vakuumimprägniertem Holz

The development of the double vacuum impregnation of doors and windows in Scandinavia shows a tendency toward larger plants. Rational production flow requirements and severe environmental pollution control require accelerated solvent evaporation from the impregnated wood. The fundamentals which are of importance to the accelerated solvent evaporation are elucidated experimentally. The principles of a practical solution are discussed including methods of air treatment.     

Auswaschung von Holzschutzmitteln im praktischen Betrieb

Practical observations indicate that rainfall on timber, freshly impregnated with water-borne preservatives, may lead to a greater preservative leaching than expected according to previous experiments. In as far as this occurs, possible reasons may be the varying work conditions in the individual impregnation plants. An eventual soil pollution would frequently be conceiled by previous accumulations. The preservative fixation under frost conditions occurs more slowly than anticipated. In contrasts, a low rainfall pH-value in the investigated region up to pH 4.5, had no influence on leaching in impregnation plants.